Gary writes, "Directly and measurably, generally not. But indirectly or more subtly, likely so. And there are plenty of reasons to think that this year's campaign could be especially sensitive to the candidates' debate performances."

"Debates have been held in nine presidential contests since 1960. We find just one after which the lead changed hands by a clearly significant margin: In 1980, when Ronald Reagan uttered his "are you better off" line. He gained 7 points in a post-debate poll."

If you don't have time for the full video, click here for a slideshow of the best debate moments from 1960 through 2004 to get up to speed before tonight!